Telephony.



E. R. CORWIN.

TELEPHONY.

APPLICATION FILED APB.. 24, 1911. RENEWED JUNE 19, 1913.

' 1,071,210, Patented Aug.26,1913.

UHF' N95. Q2

mentar.' 2577er FCO/Wav UNITED ISTATES 'PATENT OFFICE.

ELMER R. CORWIN, 0F CHICAGO. ILLINOIS, ASSIGNOR TO COR-WIN TELEPHONE MANU- FACTURING COMPANY, A' CORPORATION OF ILLINOIS.

TELEPHONY.

Specication of Letters Patent.

Application filed April 24, 191i, Serial No. $22,937. Renewed June 19, 1913. Serial No. 774,704.

To all whom, 'it may concern le it known that I, Emma li. Cona/IN, citizen of the United States, residing at (,"hivago, in the county of (look and State ot Illinois. have invented a certain new and useful improvement in Telephony` of which the following a full, clear'. eoneise, and act description, reference beingl had to the accompanying drawings, forming a part of this specification.

My inventionI relates to telephone systems and generally speaking may be described as a telephone system which includes a pinrality of telephone lines, a plurality o' trunk lines extending to the stations of said telephone lilies, apparatus whereby one sta tion, which constitutes an attendant station, may establish telephonie eonnnunimtion with the remaining stations of said tele phone lines, means whereby all of said stations may establish connection with said trunk lines, test controlling means at the stations having commimication with the attemlans station.y means at the attendants station cooperating with the latter nwans for enabling the attendant to test the liazsy or idle Condition of the trunk linei` a signal apparatus at the attendant/"s station, and means at the other stations for operating:i said signal apparatus while the ieleplninic apparatus thereat is disassociated from the trunk lines to 'furnish the attendant an aln ternative test to indicate that the stations associated with the, trunk lines desire to retain control thereof.

My invention as preferably practised ma be described a telephone system whien includes a plurality of telephone lines, a plurality of trunk lines extending to the stations of said telephone lines, apparatus whereby one station, which is an attendants station, may establish telephonie oommunication with the remaining stations of said telephone lines, means whereby all of said stations may establish connection With said trunk lines, telephone switclnhook o )erated test controlling means at the stations aving communication With the attendants station, means at the attendants station cooperating with the latter means for enabling the attendant to test the busy or idle condition ot the trunk lines, a visual signal apparatus at the attendants station, and means at the other stations for operating said visual signal apparatus While the telephonie apparatus thereat is disassociated from the trunk lines to furnish the attendant an alternative. test to indicate that the stations associated with the trunk lines desire to retain control thereat.

ll will explain my invention more fully by reference to the accom ianying drawing showing the preferred emliodlment thereof as applied to an interooinmunieating system.

l have shown three stations each having telephone lines extending to each of the other stations. The lines in the embodiment of the invention illustrated are metallic lines to whieb l do not wish to be limited. Station No 1. thus has a metallic line 11 extending therefrom to each of the other staf tions, similarly station No. Q has a telephone line 27mextending to each of the other stations, and station No. Shas a telephone line Bw-3 extending to each of the other stations. At each station there are a number of line selef'ting; keys un, one individual to each line extending to each station from another station.. whereby eaeh station may select any of the other stations, providing that the station to be selected is tree ,for selection.

Assuming that the party at some intereommunieating stations, say station No. 1, desires communication with seme other interecnm'iunicating station party, say party at station No. 2, the first or calling intercommunieating station party will first remove his telephone receiver l) from its switelnhool( thereby bridging his telephone apparatus aeross his line 1*-1, such bridge being traceable from the upper pole of the batti y e through the impedance j' of the falling line7 the right. hand armature switeh of the now denergized electro-magnet or relay g and the normal contact of sueh armature sWiteh, the transmitter L, the receiver b, the switch-hook c and the Contact directly engaged thereby, the left hand armature switch of relay g and its normal contact, a second impedance f* of the calling line, to the lower terminal of the battery e. This bridge is desirably of low resistance as compared with the resistance of the right hand winding of relay g by which charac.- teristic another line seeking line No. 1 cannot then cause the energization of the relay g belonging to such seokingline No. 1 which energization of such relay belonging to thev the right of the pins.

' seeking line is necessary .as will hereinafter appear in order to enable the seeking line to Y be telephonically connected wlth a line sought, such energization taking effect when said right hand winding of relay g belonging to a seeking line is bridged across the idle line being sought, there then belng no low shunt across the selected or called ine, the vtransmitter and receiver at the station of slch idle line being in open or very high resistance bridge. It will also later appear how the presence of the bridge establlshed at a calling station through the receiver and transmitter thereat will enable the man1- festation of a busy test signal in the telehone receiver at another station that might be seeking the first calling line.

The callin party having placed his telephone in bri ge of the line for the purposes stated, and later more fully to be explained, next fully depresses the selecting key a individual to the line of the party being called whereby the latch member k is fully de pressed owing to the engagement of the pin a1 with the inclined portion of the key a, such movement` of the latch member lc incidentally freeing the other pins a1 from engagement with the associated key plungers to enable the springs associated with any previously depressed key to restore the same to its initial position in which the pin a1 is engaged with the key notch that is located nearest the key springs. This restoring movement of a previously actuated key occurs each time any selecting key is depressed suilicientlyto carry the pin a1 below the points of the notches next adjacent and to The latch member lc carries two pins icl-k2 located above contact springs ks c, the pin k1 being closer to the spring k3 than is the pin k2 with reference to the s ring 11:4. As the latch memberc is moved downward one circuit is first estabe lished between the spring k3 and its lower or y alternate contact, and thereafter another circuit is established between the spring kt and l itslower or altennate contact. The first circuit includes the right hand high resistance coil of relay g, which coil may have a resistance say of 500 ohms, and which circuit may be traced from the upper pole of the battery e through the impedance f of line 2, the two up ermost contacts of the actuated key a, that lliey at stat-ion No. 1 which is individual to line No. 2, the said right hand high resistance winding of relay g, contact spring lcs and its alternate contact, the two lower contacts of said actuated key, the impedance l of line No.- 2, to the lower pole of the attery e. If the telephone at the called station N o. 2 is upon its hook then the bridge containing the same, which is say 50 to 100 ohms when closed, is not established across the called line so that the high resistance 66 right hand coil ofthe relay g at the calling station is not shunted by any low resistance path at the called station whereby the current from the battery is permitted to flow 1n sufficient volume through said right hand high resistance coil of the relay g, whereby the core of said coil is effectively energized and the three armature switches associated with saidvcore are operated to establish circuits which will be traced as follows:

One circuit may be traced from the upper pole of the battery e through the impedance f of the calling line, the two uppermost contacts'c1 of the switch-hook c, the left, hand coil of the relay g at the calling station No. 1 (which left hand coil may have a resistance of say 50 to 100 ohms) the intermediate armature switch of said relay, the spring c* p and its normal contact (the actuated selecting key now being released topermit the pin a1 to be bottomed in the notch nearest the key-head), the impedance f1 of the calling line to the lower pole of the battery c. When the selecting key a has been released suiiciently to occupy its interlnediate position, the circuit including the right hand coil of the relay g at statlon No. l is opened by reason of the separation of the spring ks from its alternate contact, but owing to the relationship of the springs 7c3 7c* with the pins cl k2 the circuit through the left hand coil of said relay is closed before the circuit through the right hand relay is opened during the restoring movement of the actuated selecting ke whereby the core common to the coils o the relay hold the armature switches in their positions. The relay g' at the calling station is now included in a circuit that contains the uppermost contact c1 of the switch-hook c at the calling station whereby the now only effective circuit for said relay is broken when the receiver at the calling station is restored to its switch-hook. The low resistance winding of the relay at the calling station is included in bridge of the calling' line to take the place of the bridge previously established at the calling station through the transmitter and receiver thereat, but which latter bridge has been opened by the attraction of the right hand armature switch, this latter bridge depending upon said armature switch and its normal contact for its continuity when the associate receiver is olf its hook.

When the right hand armature switch of the calling station relay is attracted no high resistance winding of the relay at any station seeking connection with line No. become energized owing to the action of said low resistance relay at the first calling station whereby the secondv calling station cannot secure telephonie connection with line N o. l. Another circuit established as a consequence of the energization of the, relay at the calling station may be traced from the upper terminal of the 1 may i shunting winding battery@ through the impedance f of the called line No. 2, the upper contact of the actuated selecting key at station No. 1 which is individual to line No. 2, the right hand 5 armature switch of the relay at the calling station and its alternate contact, the connection between said armature switch and the transmitter h, the receiver b at the calling station, the switch-hook o at the calling station, the left hand armature switch of the calling station relay, the contact spring k3 and its normal contact, the lowermost contacts of said actuated semi-restored selecting key, the impedance f1 belonging to the called line, to the lower pole of the battery e. In

this way the calling station telephone apparatus is supplied with talking battery and is transferred toa bridge connection between the sides of the called line, this transfer occurring immediately upon the release of the actuated selecting key to permit said key to occupy its intermediate position at which time the low resist-ance winding of said relay is placed in bridge of the calling line for the purposes previously stated. If the called party at station No. 2 has his telephone in use, a characteristic testing current would have flowed through the telephone receiver' `at calling station No. 1 during the time that the selecting key was fully depressed and which testing current would have vfound a circuit similar to that circuit which will hereinafter be described in connection with the telephone receiver at station No. 3 where circuit connections are shown that arise when a party seeking connection with a line across which a telephone bridge is established or the substitute for such bridge that includes the left hand low resistance winding of the relay g at the busy station being sought. The calling party at station No. 1, receiving no busy test signal, depresses his ringing key Z and thereby includes the signal or bell m at the called station in circuit with a ringing battery n, which circuit may be traced from the upper pole of the ringing battery through the contacts of the ringing key Z, the lowermost contacts of the semireleased selecting key at station No. 1, the left hand armature switch of the relay g at called station No. 2 and the normal contact of such switch, the switch-hook c at the called station and its normal contact, the signal receiver m at the called station, thence to the lower pole of said ringing battery. The party at station No. 2 removes his telephone receiver b from its switchhook, in response to the signal conveyed by the device m, and connects his transmitter and receiver in bridge of the line No. 2, whereby the transmitter at station No. 2 is supplied with battery current and telephonie connection is established with the calling partys telephone previously bridged across 55 line No. 2, it being understood that the call-l ing partys telephone bridge across line No.

2 guards line No. 2 against selection by and permitting a test signal to be furnished. to a second calling line seekingvconnectlon with line No. 2. It is understood that the called partys relay f7 remains inert throughout the entire connection as the -system is here organized.

It has been explained how the telephone receiver at station No. 1 is in bridge of the 75 line belonging to this station when the party there initiates a call and prior to the actuation of a selecting key at said station, whereby the calling line is guarded against selection by another callingparty. It has also go been explainedv how the calling partys telephone is 'placed in bridge of the called line and how a low resistance bridge including the left hand winding of the relay g at the calling station is substituted for the tele- 35 phone receiver bridge that Ahas been transferred from line No. 1 to line No. 2 whereby line No. 1 is still guarded against selection by another calling party. It will be understood that owing to the transfer ofthe call ing partys receiver to a bridge connection between the sides 2-2 of the called line, such called line is guarded by such receiver bridge. When the parties are through conversation they restore their telephone re- Yceivers to their switch-hooks, battery e being excluded from circuit with the transmitter h at the called station No. 2 and also being excluded from circuit with the transmitter h at the calling station. The only circuit 1'00 that previously remained closed for the relay g at calling station No. 1 is opened at the switch-hook c at the calling station when the telephone receiver thereat is restored thereupon. The equipments at both calling and called stations are now restored to normal so that either station may call or be selected.

I will now describe the testing circuit which prevails when the calling line seeks another line across which a low resistance bridge conductor has been placed either b the position of a telephone receiver circuit across the line or a circuit of equivalent resistance, namely, the left hand low re- 11'5 sistance winding of a relay g at another calling station. The equipment at station No. 3 is shown in the condition which it has when the parts at such station seeks connection with theline across which one of the described low resistance bridges has been placed. By way of example, the party at station No. 3 is shown in the act of endeavoring to select station No. l which was previously described as being aystation calling station No. 2. The party at station No.

3 removes his telephone from its switchhook and thereafter fully depresses the selecting key a individual to line No. 1, belonging to station No. 1 and causes the 130 establishment of a circuit that may be traced from the upper pole of the battery e, the impedance f of line No. 1, the uppermost contacts of the actuated key at station No. 3, the right hand high resistance coil of relay g at station No. 3, the contact spring c at station No. 3 and the alternate contact of such spring, the lowermost contacts of the actuated key at station No. 3, the impedance f1 of line No. l, to the lower pole of the battery e. Owing to the presence of the low resistance bridge across line No. 1 the relay g at station No. 3 will not be suiiciently energized to cause the operation of its armature switches. The party at station No. 3 also receives a busy test manifestation owing to the establishment of a circuit which may be traced from the upper pole of the battery e, the impedance f of line No. 3, the right hand armature switch of relay g at station No. 3 and the normal contact of such armature switch, the connection that intervenes between said armature switch and the transmitter L at station No. 3, the telephone receiver b at station No. 3, the switch-hook at said station, the left hand armature switch of relay g and the normal contact of such switch, the busy testcontact spring c* and its alternate contact, thence to the lower pole of the battery e by way of the device o for causing such modiiication of the current flowing from the battery e as to produce a characteristic testing current to inform seeking parties of the busy condition of the lines.` f

The apparatus at the different intercommunicating stations is thus similar in equipment, function, arrangement and circuit association and similar parts are given similar characters of reference, except certain automatic equipment indicated at t' at station No. 1 when said station is to be constituted an attendants station and is to have facilities for autol'natically selecting a called automatic line.

Station No. 1, now to be considered as an attendants station, has been shown as being a calling station with reference to station No. 2, though station No. 3 is shown as being a calling station with reference to station No. 1. Station No. l, however, is shown as being in calling or selecting relation with a trunk line (which so far as my present invention is concerned may bc either manual or automatic) and I will now describe the operations, the apparatus, and circuit changes which occur when a party at the attendants station7 No. 1 station, seeks connection by means of a trunk line with a called station.

As I have shown my invention, a plurality of trunk lines extends to each of the intercommunicating stations, selecting keys p being provided at each intercommunicating station one individual to each trunk line .1n an intermediate position as at each intercommunicating station. I have shown portions of two trunk lines fl-g and 7"-13 the line r-r being indicated as eX- tending to a jack r1 at a manual exchange while the line g-g may be assumed, for purposes of illustration, to extend to an automatic exchange.

It is assumed that the party at the attendants station, station No. 1, has been in the act of appropriating trunk line 1^ to which end such party first removed his receiver from its switch-hook at his station. By this operation the party at station No. 1 included his receiver in low resistance bridge of his line so as to guard his line and enable a busy test signal to be furnished to a party seeking his line in the manner which has been described. The calling party endeavoring to select the trunk line r next fully depresses his key p that is individual to the trunk line in order to test the trunk line. It will now be assumed that such trunk line is idle (a busy test circuit being later traced over abusy trunkI line). The seeking party at station No. 1 next releases the actuated button p to permit the spring mechanism thereof to place said key shown whereby the calling partys receiver andtransmitter are placed in bridge between the sides of the selected trunk line owing to the energi- Zation of the relay g, the left hand winding of this relay g being placed in bridge of the line 1 1, all as will readily be understood from the previous description without further explanation, the four lower contacts of each key p having the same relation with the sides of the trunk line associated therewith as is possessed by the four contacts of each selecting key a with respect to 105 the line associated therewith and also possessing similar circuit relation with respect to the associated relay g. It may be said that the only distinction between the electrical environment of each key p and each 110 key a resides in the provision of the upper contact for each key p and certain connections to be mentioned leading from said contact and to the next contact beneath. With the key p in its intermediate position, the 115 trunk line r is guarded by the telephone of station No. 1 bridged across the trunk line and line No. 1 is guarded by the left hand low resistance 'winding of the relay at station No. l bridged between its sides. At- 120 this point, it the trunk line `selected had been an automatic trunk line the attendant at station No. 1 would operate his dial mechanism i in a well known manner, such dial mechanism being very familiar to those 125 skilled in the art, and in the process of connection with an automatic called subscriber a bridge including a magnet indicated at s and batter t is established at the automatic exchange or the purpose of preventing the 130 release magnet from releasing the called automatic subscriber, all as is well understood by those skilled in the art. Where a manual trunk line is employed I may establish a ermanent bridge across the sides thereof as indicated at s1 t1, the bridge being employed for purposes stated.

Let it now be assumed that a call has come in over the trunk line in any usual way and tion No. 2. The attendant operator at station No. 1-will bring herself into communication with the party at station No. 2 and instruct such party to connect himself with atrunk line, preferably the trunk line over which the call has come. This connection with .the trunk line is there established by causing key p at station No. 2 to assume an intermediate position. If the party at station No. 2 should for any reason whatever desire to disconnect his telephone from the trunk line and at the same timeretain control over said trunk line so as' thereafter to be able to resume connection with the calling partyI over the trunk line, such party at station o. 2 will fully depress the semidepressed selecting key p and thereafter rel store his telephone receiver upon its switchhook and finally permit the said key p to become restored to its intermediate position. As a consequence of these operations relay g at station No. 2 is denergized owing to the operation of the contacts 01 at station No. 2. The relay v associated with the trunk line is bridged across the sides of the trunk line as a result of the full depression of the key p, such bridge connection being traceable from the lower side of the trunk line through the winding of t-he relay c, the two uppermost contacts of the key p at station No. 2, to the upper side of the trunk. The right hand armature of said relay u is attracted so as to maintain said bridge continuous when the keyA p is finally released, the bridge connection maintained by said right hand armature switch being traceable from the lower side of the trunk line through the winding of the relay v, said right hand switch and its contact to the upper side of the trunk line. The bridge including the elements s1 t1 being present, the y circuit for the relay 'v is maintained closed, the relay 4J then establishes,- at this left hand armature switch, a local circuit through the signal lamp ful so that the attendant will not use the appropriated trunk line for any `outgoing connections, the lamp o1 furnishing a visual test (though I do not wish to be limited to the Visual test in this connection) which visual test guards the appropriated trunk line during the time that the low resistance shunt that includes the receiver at station No. 2 and which furnishes an alternative testing facility, is removed from between the sides of the trunk line. Thus f the attendant knows absolutely whether the trunk line is busy, idle or is being held for use by an intercommunicating party. When the party at station No. 2 desires to resume the connection of his telephone with the tr'unk line, he first removes his receiver from its switch-hook, fully depresses the previously actuated key 20 and then releases said key to permit it to occupy an intermediate position. As a consequence of these operations the telephone at station No. 2 is again placed in bridge of the trunk line, the left hand winding of the relay at station "Nd 2 is again placed in bridge of line No. 2 whereby telephonie relation of station No. 2 telephone with the trunk line is maintained. The relay o being of high resistance, say 500 ohms, is now shunted y the telephone at station No. 2 so as to release the signal v1, audible test facilities now being substituted.

lVhile I have herein shown and particularly described the 'preferred embodiments of my invention I do not wish to be limited thereto as changes may be made without departing from the spirit of my invention, but

Having thus described my invention, I claim as new and desire to secure by Letters Patent the following:

l. A telephone systemy including a plurality of telephone lines, a plurality of trunk lines extending to stations of said telephone lines, apparatus whereby one station, which constitutes an attendants station, may establish telephonie communication with the remaining of said telephone line stations, means whereby all of said stations may establish connection with said trunk lines, test controlling means at the stations having communication with the attendants station, means at the attendants station coperating with the latter means for enabling the attendant to test the busy or idle condition of the trunk lines. a signal apparatus at the attendants station, and means at the other stations for operating said signal apparatus while the telephonie apparatus thereat is disassociated from the trunk lines to furnish the attendant an alternative test to indicate that the stations associated with the trunk lines desire to retain control thereof.

2. A telephone system including a plulines extending to stations of said telephone lines, apparatus whereby one station, which constitutes an attendants station, may establish telephonie communication with the remeans whereby all of said stations may establish connection with said trunk lines, telephone switch-hook operated test controlling means at the stations having communication rality of telephone lines, a pluralityof trunk maining of said telephone line stations,

with the attendants station, means at the attendants station cooperating with the latter means for enabling the attendant to test the busy or idle condition of the trunk lines, a signal apparatus at the attendants station, and means at the other stations for operating said signal apparatus While the teleplionic apparatus thereat is disassociated from the trunk lines to furnish the attendant an alternative test to indicate that the stations associated With the trunk lines desire to retain control thereof.

3. A telephone system including a plurality of telephone lines, a plurality of trunk lines extending to stations of said telephone lines, apparatus whereby one station, which constitutes an attendants station, may establish telephonie communication With the remaining of said telepho-ne line stations, means whereby all of said stations may establish connection With said trunk lines, test controlling means at the stations having communication With the attendant-s station, means at the attendants station cooperating with the latter means for enabling the attendant to test the busy or idle condition of the trunk lines, a signal apparatus at the attendants station, means at the other stations for operating said signal apparatus while the telephonie apparatus thereat is disas'sociated from the trunk lines to furnish the attendant an alternative test to indicate that the stations associated with the trunk lines desire to retain control thereof, and means for restoring signaling apparatus at the attendants station When connection is resumed with the trunk lines at the other stations.

4. A telephone system including a plurality of telephone lines, a plurality of trunk lines extending to stations of said telephone lines, apparatus whereby one station, which constitutes an attendants station, may establish telephonie communication With the remaining of said telephone line stations, means whereby all of said stations may establish connect-ion with said trunk lines, telephone sWitch-hook operated test controlling means at the stations having communication with the attendants station, means at the attendants station cooperating with the latter means for enabling the attendant to test the busy or idle condition of the trunk lines, a signal apparatus at t-he attendants station, means at the other stations for operating said signal apparatus While telephonie apparatus thereat is disassociated from the trunk lines to furnish the attendant an alternative test to indicate that the stations associated Wit-h the trunk lines desire to retain control thereof, and means for restoring signal apparatus at the attendants station when connection is resumed wit-h the trunk lines at the other stations.

In Witness whereof, I hereunto subscribe my name this twenty third day of March A. D. 1911.

ELML?, R. CORWIN. Witnesses:

Gr. L. CRAGG,

ETTA L. WHITE.

Copies of this patent may be obtained for ve cents each, by addressing the Commissioner of Patents. Washington, D. C. 

